sedimentary

Chert (Flint)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: Cream, tan, grey, or brown; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 Mohs scale
Color: Cream, tan, grey, or brown
Luster: Waxy to vitreous

Identified March 25, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: Cream, tan, grey, or brown; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine environments; often occurs as nodules in limestone or chalk beds. Geological age ranges from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools and weapons (arrowheads); currently used in road construction, as an abrasive, and occasionally in jewelry as cabochons.

Geological facts

Due to its conchoidal fracture, it produces extremely sharp edges. It was the primary material for the 'Stone Age' technology and can create sparks when struck against steel, which was used in early firearms like flintlocks.

Field identification & locations

Identify by its 'shell-like' curved (conchoidal) fractures and its ability to scratch glass. It feels smooth and waxy to the touch. Commonly found in riverbeds or eroding out of limestone cliffs in places like the UK, USA (Ohio, Texas), and France.